1. Field of the Invention
The present invention relates to a technique that detects a target object such as the face of an object from a sensed image, and displays a frame surrounding the target object together with the sensed image.
2. Description of the Related Art
Some conventional image sensing apparatuses have a face frame display function of detecting the face area of a person from an image during recording, and displaying a face frame so as to surround the detected face area, thereby allowing the user to recognize a person to be focused on and assisting recording of the person.
Japanese Patent Laid-Open No. 2005-286940 describes a technique that displays a sensed object image on the display screen of a camera, and displays a face frame so as to surround a face image portion detected from the object image, thereby allowing the user to recognize the face image portion detected during recording.
Also, Japanese Patent Laid-Open No. 2005-128156 describes a technique that detects the eye of an object contained in an image during person recording, displays a focusing frame around the detected eye, and controls auto-focusing by using the focusing frame as an in-focus position for use in recording.
Furthermore, as examples of a method of detecting a person's face area, M. A. Turk and A. P. Pentland, “Face recognition using eigenfaces”, Proc. of IEEE Conf. on Computer Vision and Pattern Recognition, pp. 586-591, 1991, describes a method using eigenfaces obtained by main component analysis, and Japanese Patent Laid-Open No. 1997-251534 describes a method using feature points such as the eye, nose, and mouth.
Unfortunately, the face detection process described above takes a long time to detect the face area from the sensed image, because the volume of calculation involved is large. When displaying the face frame on the basis of the face detection results, therefore, if a camera shake occurs on the apparatus, as shown in FIGS. 10A to 10C, updating the display position of the face frame is delayed by the time required to detect the face of an image that is moved by the camera shake. Also, especially when an image contains a plurality of faces, the time required for the face detection process further increases.
The method described in Japanese Patent Laid-Open No. 2005-128156 displays a focusing frame to make it possible to readily obtain an image of a person in which the object is focused. However, the focusing frame is based on the result of detection of the object's eye. Similar to Japanese Patent Laid-Open No. 2005-286940, therefore, if a camera shake or the like has moved an image sensing apparatus, updating the display position of the focusing frame is delayed.